Healing is basically body response to injury. Thus process to restore normal structure & function it occurs. The skin appearing afterward is different.


It generally involves two distinct processes:-

    • results in the overall restoration of original tissues.
    • markedly takes place by the proliferation of parenchymal cells.
    • occurs mainly.
    • also resulting in fibrosis and scarring.
    • thus takes place by the proliferation of connective tissue elements.


Some parenchymal cells are particularly short-lived. While others have a longer lifespan. So as to keep up the proper structure of tissues. these cells are under constant regulatory control of their cell cycle.

These include growth factors such as:

  • epidermal growth factor
  • fibroblast growth factor
  • platelet-derived growth factor
  • endothelial growth factor
  • transforming growth factor.

Depending upon their capacity to divide significantly, the cells of the body can be divided into 3 groups:

1. Labile cells. particularly multiply throughout life under normal physiologic conditions. These include the following:

  • surface epithelial cells of the epidermis
  • alimentary tract
  • respiratory tract
  • urinary tract
  • vagina
  • cervix
  • uterine endometrium
  • haematopoietic cells of bone marrow
  • cells of lymph nodes and spleen.

2. Stable cells. decrease or lose their ability to multiply after adolescence. but have the strength to multiply in response to stimuli throughout adult life. These include the following:

  • parenchymal cells of organs e.g. :
    • liver
    • pancreas
    • kidneys
    • adrenal
    • thyroid
  • mesenchymal cells e.g. :
    • smooth muscle cells
    • fibroblasts
    • vascular endothelium
    • bone and cartilage cells.

3. Permanent cells. basically lose their ability to proliferate around the time of birth. These also include:

  • neurons of nervous system,
  • skeletal muscle, and
  • cardiac muscle cells.


  1. Labile cells remain in the cell cycle i.e. from one mitosis to the next.
  2. Stable cells are in the resting phase (G0). but can be stimulated to enter the cell cycle.
  3. Permanent cells left the cell cycle and thus die after injury.
Regeneration of any type of parenchymal cells involves the following 2 processes:

i) Proliferation of original cells from the margin of injury with migration so that it cover the gap.

ii) Proliferation of migrated cells with subsequent differentiation and maturation so as to reconstitute the original one.



It’s the replacement of injured tissue by fibrous tissue during healing. Repair response takes place by the participation of the following:

  • mesenchymal cells chiefly consisting of
    • connective tissue stem cells,
    • fibrocytes, and
    • histiocytes.
  • endothelial cells
  • macrophages
  • platelets
  • and lastly parenchymal cells of the injured organ.

Two processes are involved in repair:

  1. Granulation Tissue Formation. This name arrises from the little bit granular and pink appearance of tissue. Each granule corresponds histologically to the proliferation of new small blood vessels. These appears slightly above from the surface covered by thiin fibroblasts and young collagen.
  2. Contraction of wounds. The wound starts contracting after 2-3 days. The process is completed by the 14th day. During this process, the wound is decreased by approx.80% from its original size. It results in rapid healing since the lesser surface area of the injured tissue has to be replaced.
healing: repair


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